Phosphorescent compound with fused rng substitution

ABSTRACT

Compounds including a ligand L according to Formula I devices containing the same and formulations including the same are described. 
     
       
         
         
             
             
         
       
     
     In Formula I, B is a 5 or 6-membered carbocyclic or heterocyclic ring; C is a condensed aromatic ring system having at least two carbocyclic or heterocyclic rings; A-B represents a bonded pair of carbocyclic or heterocyclic rings coordinated to a metal M via a nitrogen atom in ring A and an sp 2  hybridized atom X 6  in ring B; R A , R B  and R C  can represent no substitutions or the maximum substitutions available on the respective ring; X 1 , X 2 , X 3 , X 4 , X 5 , and X 6  are carbon or nd nitrogen, and X 7  is carbon; at least one of R A  and R C  substituents adjacent to the bond between A and C is not hydrogen; and the ligand is coordinated to a metal, having an atomic number greater than 40.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Patent Application Ser. No.61/767,508, filed Feb. 21, 2013, the entire contents of which isincorporated herein by reference.

PARTIES TO A JOINT RESEARCH AGREEMENT

The claimed invention was made by, on behalf of and/or in connectionwith one or more of the following parties to a joint universitycorporation research agreement: Regents of the University of Michigan,Princeton University, University of Southern California, and theUniversal Display Corporation. The agreement was in effect on and beforethe date the claimed invention was made, and the claimed invention wasmade as a result of activities undertaken within the scope of theagreement.

FIELD OF THE INVENTION

The present invention relates to compounds for use as emitters anddevices, such as organic light emitting diodes, including the same.

BACKGROUND

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting devices (OLEDs), organic phototransistors, organic photovoltaiccells, and organic photodetectors. For OLEDs, the organic materials mayhave performance advantages over conventional materials. For example,the wavelength at which an organic emissive layer emits light maygenerally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Color may be measured using CIE coordinates, which are wellknown to the art.

One example of a green emissive molecule is tris(2-phenylpyridine)iridium, denoted Ir(ppy)₃, which has the following structure:

In this, and later figures herein, we depict the dative bond fromnitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large. Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone. Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processible” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital”0 (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled inthe art, a first work function is “greater than” or “higher than” asecond work function if the first work function has a higher absolutevalue. Because work functions are generally measured as negative numbersrelative to vacuum level, this means that a “higher” work function ismore negative. On a conventional energy level diagram, with the vacuumlevel at the top, a “higher” work function is illustrated as furtheraway from the vacuum level in the downward direction. Thus, thedefinitions of HOMO and LUMO energy levels follow a different conventionthan work functions.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

SUMMARY OF THE INVENTION

According to an embodiment, a compound is provided that includes aligand L having the structure according to Formula I:

In Formula I:

-   -   B is a 5 or 6-membered carbocyclic or heterocyclic ring;    -   C is a condensed aromatic ring system having at least two        carbocyclic or heterocyclic rings;    -   A-B represents a bonded pair of carbocyclic or heterocyclic        rings coordinated to a metal M via a nitrogen atom in ring A and        an sp² hybridized atom X⁶ in ring B;    -   A-C represents a bonded, pair of carbocyclic or heterocyclic        rings;    -   R^(A) may represent mono, di, or tri substitutions, or no        substitution;    -   R^(B) may represent any number of substitution from mono to up        to the maximum possible number of substitution on ring B, or no        substitution;    -   R^(C) may represent any number of substitution from mono to up        to the maximum possible number of substitution on ring C, or no        substitution;    -   R^(A), R^(B), and R^(C) are independently selected from the        group consisting of hydrogen, deuterium, halide, alkyl        cycloalkyl, heteroalkyl, aralkyl, alkoxy, aryloxy, amino, silyl,        alkenyl, cycloalkenyl, heteroalkenyl alkynyl, aryl, heteroaryl,        acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile,        sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations        thereof;    -   X¹, X², X³, X⁴, X⁵, and X⁶ are independently selected from        carbon and nitrogen;    -   X⁷ is carbon;    -   at least one of R^(A) and R^(C) substituents adjacent to the        bond between A and C is not hydrogen; and    -   the ligand L is coordinated to the metal M having an atomic        number greater than 40.

According to another embodiment, a first device comprising a firstorganic light emitting device is also provided. The first device caninclude an anode, a cathode, and an organic layer, disposed between theanode and the cathode. The organic layer can include a compoundincluding a ligand of Formula I. The first device can be a consumerproduct, an organic light-emitting device, and/or a lighting panel.

According to still another embodiment, a formulation that includes acompound including a ligand of Formula I is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does nothave a separate electron transport layer.

FIG. 3 shows Formula I as disclosed herein.

FIG. 4 shows Formula II as disclosed herein.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example. In U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 15-154, 1998; (“Baldo-I”)and Baldo et al., “Very high-efficiency green organic light-emittingdevices based on electrophosphorescene,” Appl. Phys. Lett., vol. 75, No.3, 4-6 (1999) (“Baido-II”), which are incorporated by reference in theirentireties. Phosphorescence is described in more detail in U.S. Pat. No.7,279,704 at cols. 5-6, which are incorporated by reference.

FIG. 1 shows an organic light emitting device 100. The figures are notnecessarily drawn to scale. Device 100 may include a substrate 110, ananode 115, a hole injection layer 120, a hole transport layer 125, anelectron blocking layer 130, an emissive layer 135, a hole blockinglayer 140, an electron transport layer 145, an electron injection layer150, a protective layer 155, a cathode 160, and a barrier layer 170.Cathode 160 is a compound cathode having a first conductive layer 162and a second conductive layer 164. Device 100 may be fabricated bydepositing the layers described, in order. The properties and functionsof these various layers, as well as example materials, are described inmore detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which areincorporated by reference.

More examples tor each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F₄-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of emissive and host materials aredisclosed in U.S. Pat. No. 6,303,238 to Thompson et. al., which isincorporated by reference in its entirety. An example of an n-dopedelectron transport layer is BPhen doped with Li at a molar ratio of 1:1,as disclosed in U.S. Patent Application Publication No. 2003/0230980,which is incorporated by reference in its entirety. U.S. Pat. Nos.5,703,436 and 5,707,745, which are incorporated by reference in theirentireties, disclose examples of cathodes including compound cathodeshaving a thin layer of metal such as Mg:Ag with, an overlyingtransparent, electrically-conductive, sputter-deposited ITO layer. Thetheory and use of blocking layers is described in more detail in U.S.Pat. No. 6,097,147 and U.S. Patent Application Publication No.2003/0230980, which are incorporated by reference in their entireties.Examples of injection layers are provided in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety. A description of protective layers may be found in U.S. PatentApplication Publication No. 2004/0174116, which is incorporated byreference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 maybe fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved, by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as & hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such asdisclosed, in U.S. Pat. No. 5,247,190 to Friend et al., which isincorporated by reference in its entirety. By way of further example,OLEDs having a single organic layer may be used. OLEDs may be stacked,for example as described in U.S. Pat. No. 5,707,745 to Forrest et al,which is incorporated by reference in its entirety. The OLED structuremay deviate from the simple layered structure illustrated in FIGS. 1 and2. For example, the substrate may include an angled reflective surfaceto improve out-coupling, such as a mesa structure as described in U.S.Pat. No. 6,091,195 to Forrest et al., and/or a pit structure asdescribed in U.S. Pat. No. 5,834,893 to Bulovie et al., which areincorporated by reference In their entireties.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. For the organic layers,preferred methods include, thermal evaporation, ink-jet, such asdescribed in U.S. Pat. Nos. 6,013,982 and 6,087,196, which areincorporated by reference in their entireties, organic vapor phasedeposition (OVPD), such as described in U.S. Pat. No. 6,337,102 toForrest et al., which is incorporated by reference in its entirety, anddeposition by organic vapor jet printing (OVJP), such as described inU.S. Pat. No. 7,431,968, which is incorporated by reference in itsentirety. Other suitable deposition, methods include spin coating andother solution based processes. Solution based processes are preferablycarried out in nitrogen or an inert atmosphere. For the other layers,preferred methods include thermal evaporation. Preferred patterningmethods include deposition through a mask, cold welding such asdescribed in U.S. Pat. Nos. 6,294,398 and 6,468,819, which areincorporated by reference in their entireties, and patterning associatedwith some of the deposition methods such as ink-jet and OVID. Othermethods may also be used. The materials to be deposited may be modifiedto make them compatible with a particular deposition method. Forexample, substituents such as alkyl and aryl groups, branched orunbranched, and preferably containing at least 3 carbons, may be used insmall molecules to enhance their ability to undergo solution processing.Substituents having 20 carbons or more may be used, and 3-20 carbons isa preferred range. Materials with asymmetric structures may have bettersolution processibility than those having symmetric structures, becauseasymmetric materials may have a lower tendency to recrystallize.Dendrimer substituents may be used to enhance the ability of smallmolecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the presentinvention may further optionally comprise a barrier layer. One purposeof the barrier layer is to protect the electrodes and organic layersfrom damaging exposure to harmful species in the environment includingmoisture, vapor and/or gases, etc. The barrier layer may be depositedover, under or next to a substrate, an electrode, or over any otherparts of a device including an edge. The barrier layer may comprise asingle layer, or multiple layers. The barrier layer may be formed by-various known chemical vapor deposition techniques and may includecompositions having a single phase as well as compositions havingmultiple phases. Any suitable material or combination of materials maybe used for the barrier layer. The barrier layer may incorporate aninorganic or an organic compound or both. The preferred barrier layercomprises a mixture of a polymeric material and a non-polymericmaterial, as described in U.S. Pat. No. 7,968,146, PCT Pat. Application.Nos. PCT/US2007/023098 and PCT/US2009/042829, which are hereinincorporated by reference in their entireties. To be considered a“mixture”, the aforesaid polymeric and non-polymeric materialscomprising the barrier layer should be deposited under the same reactionconditions and/or at the same time. The weight ratio of polymeric tonon-polymeric material may be in the range of 95:5 to 5:95. Thepolymeric material and the non-polymeric material may he created fromthe same precursor material. In one example, the mixture of a polymericmaterial and a non-polymeric material consists essentially of polymericsilicon and inorganic silicon.

Devices fabricated in accordance with embodiments of the invention maybe incorporated into a wide variety of consumer products, including fiatpanel displays, computer monitors, medical monitors, televisions,billboards, lights for interior or exterior illumination and/orsignaling, heads up displays, fully transparent displays, flexibledisplays, laser printers, telephones, cell phones, personal digitalassistants (PDAs), laptop computers, digital cameras, camcorders,viewfinders, micro-displays. 3-D displays, vehicles, a large area wall,theater or stadium screen, or a sign. Various control mechanisms may beused to control devices fabricated in accordance with the presentinvention, including passive matrix and active matrix. Many of thedevices are intended for use in a temperature range comfortable tohumans, such as 18 degrees C. to 30 degrees C., and more preferably atroom temperature (20-25 degrees C.), but could he used outside thistemperature range, for example, from −40 degree C. to +80 degree C.

The materials and structures described herein may have applications indevices other than OLEDs. For example, other optoelectronic devices suchas organic solar cells and organic photodetectors may employ thematerials and structures. More generally, organic devices, such asorganic transistors, may employ the materials and structures.

The terms halo, halogen, alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl,heterocyclic group, aryl, aromatic group, and heteroaryl are known tothe art, and are defined in U.S. Pat. No. 7,279,704 at cols. 31-32,which are incorporated herein by reference.

As used herein, “substituted” indicates that a substituent other than His bonded to the relevant carbon. Thus, where R^(B) is monosubstituted,then one R^(B) must he other than H. Similarly, where R^(C) isdisubstituted, then two of R^(C) must be other than H. Similarly, whereR^(B) is unsubstituted R^(B) is hydrogen for all available positions.

According to an embodiment, phosphorescent compounds with fused ringsubstitutions that are unexpectedly suited as yellow and green emittersare provided. In has been unexpectedly determined that attaching apendant fused ring on Ring A of compounds of Formula I, produces a newclass of yellow/green phosphorescent emitters exhibiting improvedproperties. Comparable compounds exhibited an undesirable red shift sothis result was completely unexpected.

For example, it was disclosed in US2011227049 that the followingcompound gave a green emission at around 528 nm.

Without the methyl substitution, the compound gave a yellow emission ataround 545 nm. The methyl substitution twisted the phenyl group out ofplane and disrupted the conjugation, giving a much blue shiftedemission. In. the compounds described herein, a fused ring substitutionwas introduced instead of the phenyl group. Fused aromatic or heteroaromatic substitution has lower triplet values and is expected tosignificantly red shift the emission compared to the phenylsubstitution. However, it was discovered that these compounds did notshow significant red shift, which unexpectedly makes them viablecandidates as green phosphorescent emitters.

According to one embodiment, a compound comprising a ligand L having thestructure according to Formula I is provided:

-   -   wherein B is a 5 or 6-membered carbocyclic or heterocyclic ring;    -   wherein C is a condensed aromatic ring system having at least        two carbocyclic or heterocyclic rings;    -   wherein A-B represents a bonded pair of carbocyclic or        heterocyclic rings coordinated to a metal M via a nitrogen atom        in ring A and an sp² hybridized atom X⁶ in ring B;    -   wherein A-C represents a bonded pair of carbocyclic or        heterocyclic rings;    -   wherein R^(C) may represent mono, di, or tri substitutions, or        no substitution;    -   wherein R^(B) may represent any number of substitution from mono        to up to the maximum possible number of substitution on ring B,        or no substitution;    -   wherein R^(C) may represent any number of substitution from mono        to up to the maximum possible number of substitution on ring C,        or no substitution;    -   wherein R^(A), R^(B), and R^(C) are independently selected from        the group consisting of hydrogen, deuterium, halide, alkyl,        cycloalkyl, heteroalkyl, aralkyl, alkoxy, aryloxy, amino, silyl,        alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,        acyl, carbonyl, carboxylic acids, ester, nitrite, isonitrile,        sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations        thereof;    -   wherein X¹, X², X³, X⁴, X⁵, and X⁶ are independently selected        from carbon and nitrogen;    -   wherein X⁷ is carbon;    -   wherein at least one of R^(A) and R^(C) substituents adjacent to        the bond between A and C is not hydrogen; and    -   wherein the ligand L is coordinated to the metal M having an.        atomic number greater than 40.

In some embodiments, ring A can be pyridine. In some embodiments, ring Bcan be phenyl.

In. some embodiments, only one of the R^(A) and R^(C) substituentsadjacent to the bond between A and C is not hydrogen. In someembodiments, the R^(A) and R^(C) substituents adjacent to the bondbetween A and C are selected from the group consisting of hydrogen;deuterium; linear, branched and cyclic alkyl; and combinations thereof.The R^(A) and R^(C) substituents adjacent to the bond between A and Ccan be selected from the group consisting of hydrogen, deuterium,methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl,2-methylpropyl, pentyl 1-methylbutyl, 2-methylbutyl, 3-methylbutyl,1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, cyclopentyl,cyclohexyl, and combinations thereof. In some instances, the only one ofR^(A) and R^(C) substituents adjacent to the bond between A and C thatis not hydrogen, can be selected from the group consisting of deuterium,methyl, ethyl, and combinations thereof.

In some embodiments, the compound can have the formula:

-   -   wherein L′ is monoanionic bidentate ligand; and    -   wherein n is at least 1.

In some embodiments, n is 1, while n can be 2 in other embodiments.

In some more specific embodiments, L′ can be selected from the groupconsisting of:

wherein: Y₁, Y₂ and Y₃ are C or N,

-   -   ring E and ring F are 5-membered or 6-membered carbocycle or        heterocycle,    -   R′, R″, and R′″ are independently selected from the group        consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl,        aralkyl, aryl, and heteroaryl,    -   X is selected from the group consisting of S, NZ, O, Se, BZ,        CZZ′, and C=O,    -   Z and Z′ are independently selected from the group consisting of        hydrogen, alkyl, and aryl, and

R′, R″, and R′″ can join to form one or more fused rings.

In some particular embodiments, L′ can be

In some embodiments, the compounds described herein can be heteroleptic,while the compounds can be homoleptic in other embodiments. In someembodiments, the bond between A and C can be formed between X² and X⁷(meta substitution relative to N in ring A), in other embodiments, thebond between A and C can be formed between X³ and X⁷ (para substitutionrelative to N in ring A).

In some embodiments, ring C can be selected from the group consistingof:

-   -   wherein A¹ to A⁸, Q¹ to Q⁶, B¹ to B⁸, J¹ to J¹², K¹ to K¹⁰ are        independently selected from the group consisting of C and N;    -   wherein X and Y are independently selected from the group        consisting of O, S, NR′, and CR″R′″; and    -   wherein R′, R″, and R′″ are independently selected from the        group consisting of hydrogen, deuterium, halide, alkyl,        cycloalkyl, heteroalkyl, aralkyl, alkoxy, aryloxy, amino, silyl,        alkenyl, cycloalkenyl, heteroalkenyl alkynyl, aryl, heteroaryl,        acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile,        sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations        thereof.

In some more specific embodiments, ring C can be selected from the groupconsisting of:

In some specific embodiments, the compound can be selected from thegroup consisting of:

According to another aspect of the present disclosure, a first device isalso provided. The first device includes a first organic light emittingdevice, that includes an anode, a cathode, and an organic layer disposedbetween the anode and the cathode. The organic layer may include a hostand a phosphorescent dopant. The organic layer can include a compoundhaving a ligand L according to Formula I, and its variations asdescribed herein.

The first device can be one or more of a consumer product, an organiclight-emitting device and a lighting panel. The organic layer can be anemissive layer and the compound can be an emissive dopant in someembodiments, while the compound can he a non-emissive dopant in otherembodiments.

In some embodiments, the organic layer can include a host. In someembodiments, the host can include a metal, complex. The host can be atriphenylene containing benzo-fused thiophene or benzo-fused furan. Anysubstituent in the host can be an unfused substituent independentlyselected from the group consisting of C_(nH) _(2n+1), OC_(n)H_(2n+1),OAr₁,N(C_(n)H_(2n+1))₂. N(Ar₁(Ar₂), CH=CH—C_(n)H_(2n+1),C≡C—C_(n)H_(2n+1), Ar₁, AR₁-Ar₂, C_(n)H_(2n)-Ar₁, or no substitution. Inthe preceding substituents n can range from 1 to 10; and Ar₁ and Ar₂ canbe independently selected from the group consisting of benzene,biphenyl, naphthalene, triphenylene, carbazole, and heteroaromaticanalogs thereof.

The host can be a compound selected from the group consisting ofcarbazole, dibenzothiphene, dibenzofuran, dibenzoselenophene,azacarbazole, aza-dibenzothiophene, aza-dibenzofuran, andaza-dibenzoselenophene. The “aza” designation in the fragments describedabove, i.e., aza-dibenzofuran, aza-dibenzonethiophene, etc., means thatone or more of the C—H groups in the respective fragment can be replacedby a nitrogen atom, for example, and without any limitation,azatriphenylene encompasses both dibenzo[f,h]quinoxaline anddibenzo[f,h]quinoline. One of ordinary skill in the art can readilyenvision other nitrogen analogs of the aza-derivatives described above,and all such analogs are intended to be encompassed by the terms as setforth herein. The host can include a metal complex. The host can be aspecific compound selected from the group consisting of:

and combinations thereof.

In yet another aspect of the present disclosure, a formulation thatincludes a compound having a ligand L according to Formula I, and itsvariations as described herein. The formulation can include one or morecomponents selected from the group consisting of a solvent, a host, ahole injection material, bole transport material, an electron transportlayer material (see below).

Combination with other Materials

The materials described herein as useful for a particular layer in anorganic light emitting device may be used in combination with a widevariety of other materials present in the device. For example, emissivedopants disclosed herein may be used in conjunction with a wide varietyof hosts, transport layers, blocking layers, injection layers,electrodes and other layers that may be present. The materials describedor referred to below are non-limiting examples of materials that may beuseful in combination with the compounds disclosed herein, and one ofskill in the art can readily consult the literature to identify othermaterials that may be useful in combination.

HIL/HTL

A hole injecting/transporting material to be used in the presentinvention Is not particularly limited, and any compound may be used aslong as the compound is typically used as a hole injecting/transportingmaterial. Examples of the material include, but not limit to: aphthalocyanine or porphryin derivative; an aromatic amine derivative; anindolocarbazole derivative; a polymer containing fluorohydrocarbon; apolymer with conductivity dopants; a conducting polymer, such asPEDOT/PSS; a self-assembly monomer derived from compounds such asphosphonic acid and silane derivatives; a metal oxide derivative, suchas MoO_(x); a p-type semiconducting organic compound, such as1,4,5,8,9,12-Hexaaxatriphenylenehexacarbonitrile; a metal complex, andacross-linkable compounds.

Examples of aromatic amine derivatives used in HIL, or HTL include, butnot limit to the following general structures:

Each of Ar¹ to A⁹ is selected from the group consisting aromatichydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl,triphenylene, naphthalene, anthracene, phenalene, phenanthrene,fluorene, pyrene, chrysene, perylene, azulene; group consisting aromaticheterocyclic compounds such as dibenzothiophene, dibenzofuran,dihenzoselenophene. furan, thiophene, benzofuxan, benzothiophene,benzoselenophene, carbazole, indolocarbazole, pyridylindole,pyrrolodipyrldine, pyrazole, imidazole, triazole, oxazole, thiazole,oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine,pyriraidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine,indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole,henzothiazole, qninoline, isoquinoline, cinnoline, quinazoline,quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine,phenazine, phenothiazine, phenoxazine, benzofuropyridine,furodipyridine, benzothienopyridine, thienodipyridine,benzoselenophenopyridine, and selenophenodipyridine; and groupconsisting 2 to 10 cyclic structural units which are groups of the sametype or different types selected from the aromatic hydrocarbon cyclicgroup and the aromatic heterocyclic group and are bonded to each otherdirectly or via at least one of oxygen atom, nitrogen atom, sulfur atom,silicon atom, phosphorus atom, boron atom, chain structural unit and thealiphatic cyclic group. Wherein each Ar is further substituted by asubstituent selected from the group consisting of hydrogen, deuterium,halide, alkyl, cycloalkyl, heteroalkyl, aralkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrite, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof.

In one aspect, Ar¹ to Ar⁹ is independently selected from the groupconsisting of:

k is an integer from 1 to 20; X¹⁰¹ to X¹⁰⁸ is C (including CH) or N;Z¹⁰¹ is NAr¹, O, or S; Ar¹ has the same group defined above.

Examples of metal complexes used in HIL or HTL include, but not limit tothe following general formula:

Met is a metal, which can have an atomic weight greater than 40;(Y¹⁰¹-Y¹⁰²) is a bidentate ligand, Y¹⁰¹ and Y¹⁰² are independentlyselected from C, N, O, P, and S; L¹⁰¹ is an ancillary ligand; k′ is aninteger value from 1 to the maximum number of ligands that may beattached to the metal; and k′+k″ is the maximum number of ligands thatmay be attached to the metal.

In one aspect, (Y¹⁰¹-Y¹⁰²) is a 2-phenylpyridine derivative.

In another aspect, (Y¹⁰¹-Y¹⁰²) is a carbene ligand.

In another aspect, Met is selected from Ir, Pt, Os, and Zn.

In a further aspect, the metal complex has a smallest oxidationpotential in solution vs. Fc⁺/Fc couple less than about 0.6 V.

Host

The light emitting layer of the organic EL device of the presentinvention preferably contains at least a metal complex as light emittingmaterial, and may contain a host material using the metal complex as adopant material. Examples of the host material are not particularlylimited, and any metal complexes or organic compounds may be used aslong as the triplet energy of the host is larger than that of thedopant. While the Table below categorizes host materials as preferredfor devices that emit various colors, any host material may be used withany dopant so long as the triplet criteria is satisfied.

Examples of metal complexes used as host are preferred to have thefollowing general formula:

Met is a metal; (Y¹⁰³-Y¹⁰⁴) is a bidentate ligand, Y¹⁰³ and Y¹⁰⁴ areindependently selected from C, N, O, P, and S; L¹⁰¹ is an anotherligand: k′ is an integer value from 1 to the maximum number of ligandsthat may be attached to the metal; and k′+k″ is the maximum number ofligands that may be attached to the metal.

In one aspect, the metal, complexes are:

(O—N) is a bidentate ligand, having metal, coordinated to atoms O and N.

In another aspect, Met is selected from Ir and Pt.

In a further aspect, (Y¹⁰³-Y¹⁰⁴) is a carbene ligand.

Examples of organic compounds used as host are selected from the groupconsisting aromatic hydrocarbon, cyclic compounds such as benzene,biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene,phenanthrene, fluorene, pyrene, chrysene, perylene, azulene: groupconsisting aromatic heterocyclic compounds such as dibenzothiophene,dibenzofuran, dibenzoselenophene, furan, thiopnene, benzofuran,benzothiopbene, benzoselenophene, carbazole, indolocarbazole,pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole,oxazoie, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole,pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine,oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine,benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline,cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine,pteridine, xanthene, acridine, phenazine. phenothiazine, phenoxazine,benzofuropyridine, furodipyridine, benxothienopyridine,thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine;and group consisting 2 to 10 cyclic structural units which are groups ofthe same type or different types selected from the aromatic hydrocarboncyclic group and the aromatic heterocyclic group and are bonded to eachother directly or via at least one of oxygen atom, nitrogen atome,sulfur atom, silicon atom, phosphorus atom, boron atom, chain structuralunit and the aliphatic cyclic group. Wherein each group is furthersubstituted by a substituent selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, aralkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl sulfonyl phosphino, andcombinations thereof.

In one aspect, host compound contains at least one of the followinggroups in the molecule:

R¹⁰¹ to R¹⁰⁷ is independently selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, aralkyl,alkoxy, atyloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof, when it is aryl or heteroaryl, it has the similardefinition as Ar's mentioned above.

k is an integer from 0 to 20 or 1 to 20; k′″ is an integer from 0 to 20.

X¹⁰¹ to X¹⁰⁸ is selected from C (including CH) or N.

Z¹⁰¹ and Z¹⁰² is selected from NR¹⁰¹, O, or S.

HBL

A hole blocking layer (HBL) may be used to reduce the number of holesand/or excitons that leave the emissive layer. The presence of such ablocking layer in a device may result in substantially higherefficiencies as compared to a similar device lacking a blocking layer.Also, a blocking layer may be used to confine emission to a desiredregion of an OLED.

In one aspect, compound used in HBL contains the same molecule or thesame functional groups used as host described above.

In another aspect, compound used in HBL contains at least one of thefollowing groups in the molecule:

k is an integer from 1 to 20; L¹⁰¹ is an another ligand, k′ is aninteger from 1 to 3.

ETL

Electron, transport layer (ETL) may include a material capable oftransporting electrons. Electron transport layer may be intrinsic(undoped), or doped. Doping may be used to enhance conductivity.Examples of the ETL material are not particularly limited, and any metalcomplexes or organic, compounds may be used as long as they aretypically used to transport electrons.

In one aspect, compound used in ETL contains at least one of thefollowing groups in the molecule:

R¹⁰¹ is selected from the group consisting of hydrogen, deuterium,halide, alkyl, cycloalkyl, heteroalkyl, aralkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrite, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof, when it is arylor heteroaryl, it has the similar definition as Ar's mentioned above.

Ar¹ to Ar³ has the similar definition as Ar's mentioned above.

k is an integer from 1 to 20.

X¹⁰¹ to X¹⁰⁸ is selected, from C (including CH) or N.

In another aspect, the metal complexes used in ETL contain, but notlimit to the following general formula:

(O—N) or (N—N) is a bidentate ligand, having metal coordinated to atomsO, N or N, N; L¹⁰¹ is another ligand; k′ is an integer value from 1 tothe maximum number of ligands that may be attached to the metal.

In any above-mentioned compounds used in each layer of the OLED device,the hydrogen atoms can be partially or fully deuterated. Thus, anyspecifically listed substituent, such as, without limitation, methyl,phenyl, pyridyl, etc. encompasses undeuterated, partially deuterated,and fully deuterated versions thereof. Similarly, classes ofsubstituents such as, without limitation, alkyl, aryl, cycloalkyl,heteroaryl, etc. also encompass undeuterated, partially deuterated, andfully deuterated versions thereof.

In addition to and/or in combination with the materials disclosedherein, many hole injection materials, hole transporting materials, hostmaterials, dopant materials, exiton/hole blocking layer materials,electron transporting and electron injecting materials may he used in anOLED. Non-limiting examples of the materials that may be used in an OLEDin combination with materials disclosed herein are listed in Table 1below. Table 1 lists non-limiting classes of materials, non-limitingexamples of compounds for each class, and references that disclose thematerials.

TABLE 1 MATERIAL EXAMPLES OF MATERIAL PUBLICATIONS Hole injectionmaterials Phthalocyanine and porphryin compounds

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J. Lumin. 72-74, 985 (1997) CF_(x) Fluorohydrocarbon polymer

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EP1725079A1 and

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US20020158242 Metal organometallic complexes

US20060240279 Cross-linkable compounds

US20080220265 Polythiophene based polymers and copolymers

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EP650955

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US20070278938, US20080106190 US20110163302 Indolocarbazoles

Synth. Met. 111, 421 (2000) Isoindole compounds

Chem. Mater. 15, 3148 (2003) Metal carbene complexes

US20080018221 Phosphorescent OLED host materials Red hostsArylcarbazoles

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Nature 395, 151 (1998)

US20060202194

WO2005014551

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Org. Electron. 1, 15 (2000) Aromatic fused rings

WO2009066779, WO2009066778, WO2009063833, US20090045731, US20090045730,WO2009008311, US20090008605, US20090009065 Zinc complexes

WO2010056066 Chrysene based compounds

WO2011086863 Green hosts Arylcarbazoles

Appl. Phys. Lett. 78, 1622 (2001)

US20030175553

WO2001039234 Aryltriphenylene compounds

US20060280965

US2006280965

WO2009021126 Poly-fused heteroaryl compounds

US20090309488 US20090302743 US20100012931 Donor acceptor type compounds

WO2008056746

WO2010107244 Aza-carbazole/DBT/DBF

JP2008074939

US20100187984 Polymers (e.g., PVK)

Appl. Phys. Lett. 77, 2280 (2000) Spirofluorene compounds

WO2004093707 Metal phenoxybenzooxazole compounds

WO2005089025

WO2006132173

JP200511610 Spirofluorene-carbazole compounds

JP2007254297

JP2007254297 Indolocabazoles

WO2007063796

WO2007063754 5-member ring electron deficient heterocycles (e.g.,triazoles, oxadiazole)

J. Appl. Phys. 90, 5048 (2001)

WO2004107822 Tetraphenylene complexes

US20050112407 Metal phenoxypyridine compounds

WO2005030900 Metal coordination complexes (e.g., Zn, Al withN{circumflex over ( )}N ligands)

US20040137268, US20040137267 Blue hosts Arylcarbazoles

Appl. Phys. Lett. 82, 2422 (2003)

US20070190359 Dibenzothiophene/ Dibenzofuran-carbazole compounds

WO2006114966, US20090167162

US20090167162

WO2009086028

US20090030202, US20090017330

US20100084966 Silicon aryl compounds

US20050238919

WO2009003898 Silicon/Germanium aryl compounds

EP2034538A Aryl benzoyl ester

WO2006100298 Carbazole linked by non- conjugated groups

US20040115476 Aza-carbazoles

US20060121308 High triplet metal organometallic complex

US7154114 Phosphorescent dopants Red dopants Heavy metal prophyrins(e.g., PtOEP)

Nature 395, 151 (1998) Iridium(III) organometallic complexes

Appl. Phys. Lett. 78, 1622 (2001)

US2006835469

US2006835469

US20060202194

US20060202194

US20070087321

US20080261076 US20100090591

US20070087321

Adv. Mater. 19, 739 (2007)

WO2009100991

WO2008101842

US7232618 Platinum(II) organometallic complexes

WO2003040257

US20070103060 Osminum(III) complexes

Chem. Mater. 17, 3532 (2005) Rutheniium(II) complexes

Adv. Mater. 17, 1059 (2005) Rhenium (I), (II), and (III) complexes

US20050244673 Green dopants Iridium(III) organometallic complexes

Inorg. Chem. 40, 1704 (2001) and its derivatives

US20020034656

US7332232

US20090108737

WO2010028151

EP1841834B

US20060127696

US20090039776

US6921915

US20100244004

US6687266

Chem. Mater. 16, 2480 (2004)

US20070190359

US 20060008670 JP2007123392

WO2010086089, WO2011044988

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Angew. Chem. Int. Ed. 2006, 45, 7800

WO2009050290

US20090165846

US20080015355

US20010015432

US20100295032 Monomer for polymeric metal organometallic compounds

US7250226, US7396598 Pt(II) organometallic complexes, includingpolydentated ligands

Appl. Phys. Lett. 86, 153505 (2005)

Appl. Phys. Lett. 86, 153505 (2005)

Chem . Lett. 34, 592 (2005)

WO2002015645

US20060263635

US20060182992 US20070103060 Cu complexes

WO2009000673

US20070111026 Gold complexes

Chem. Commun. 2906 (2005) Rhenium(III) complexes

Inorg. Chem. 42, 1248 (2003) Osmium(II) complexes

US7279704 Deuterated organometallic complexes

US20030138657 Organometallic complexes with two or more metal centers

US20030152802

US7090928 Blue dopants Iridium(III) organometallic complexes

WO2002002714

WO2006009024

US20060251923 US20110057559 US20110204333

US7393599, WO2006056418, US20050260441, WO2005019373

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Chem. Mater, 18, 5119 (2006)

Inorg. Chem. 46, 4308 (2007)

WO2005123873

WO2005123873

WO2007004380

WO2006082742 Osmium(II) complexes

US7279704

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Appl. Phys. Lett. 74, 1361 (1999) Platinum(II) complexes

WO2006098120, WO2006103874 Pt tetradentate complexes with at least onemetal- carbene bond

US7655323 Exciton/hole blocking layer materials Bathocuprine compounds(e.g., BCP, BPhen)

Appl. Phys. Lett. 75, 4 (1999)

Appl. Phys. Lett. 79, 449 (2001) Metal 8-hydroxyquinolates (e.g., BAlq)

Appl. Phys. Lett. 81, 162 (2002) 5-member ring electron deficientheterocycles such as triazole, oxadiazole, imidazole, benzoimidazole

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US20050025993 Fluorinated aromatic compounds

Appl. Phys. Lett. 79, 156 (2001) Phenothiazine-S-oxide

WO2008132085 Silylated five-membered nitrogen, oxygen, sulfur orphosphorus dibenzoheterocycles

WO2010079051 Aza-carbozoles

US20060121308 Electron transporting materials Anthracene- benzoimidazolecompounds

WO2003060956

US20090179554 Aza triphenylene derivatives

US20090115316 Anthracene-benzothiazole compounds

Appl. Phys. Lett. 89, 063504 (2006) Metal 8-hydroxyquinolates (e.g.,Alq₃, Zrq₄)

Appl. Phys. Lett. 51, 913 (1987) US7230107 Metal hydroxybenoquinolates

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Appl. Phys. Lett. 91, 263503 (2007)

Appl. Phys. Lett. 79, 449 (2001) 5-member ring electron deficientheterocycles (e.g., triazole, oxadiazole, imidazole, benzoimidazole)

Appl. Phys. Lett. 74, 865 (1999)

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Experimental Device Examples

All example devices were fabricated by high, vacuum (<10⁻⁷ Torr) thermalevaporation. The anode electrode was 1200 Å of indium tin oxide (ITO).The cathode consisted of 10 Å of LiF followed by 1,000 Å of Al. Alldevices were encapsulated with a glass lid sealed with an epoxy resin ina nitrogen glove box (<1 ppm of H₂O and O₂) immediately afterfabrication, and a moisture getter was incorporated Inside the package.

The organic stack of the device examples consisted of sequentially, fromthe ITO surface, 100 Å of Compound A as the hole injection layer (HIL),300 Å of 4,4′-bis[N-(1- naphthyl)-N-phenylamino]biphenyl (α-NPD) as thehole transporting layer (HTL), 300 Å of the inventive compounds dopedwith Compound B as host, with 8-10 wt % of the iridium phosphorescentcompound as the emissive layer (EML), 50 or 100 Å of Compound B as ablocking layer (BL), 400 or 450 Å of Alq (tris-8-hydroxyquinolinealuminum) as the ETL. The comparative Examples were fabricated similarlyto the Device Examples except that Compound A was used as the emitter inthe EML.

The device results and data are summarized in Tables 1 and 2 from thosedevices.

TABLE 1 device Structures of Inventive Compound and Comparative CompoundHIL HTL EML Example (100 Å) (300 Å) (300 Å, doping %) BL ETL Example 1Compound A NPD Compound 1 (10%) Compound B Alq  (50 Å) (450 Å) Example 2Compound A NPD Compound 2 (10%) Compound B Alq  (50 Å) (450 Å) Example 3Compound A NPD Compound 20 (10%) Compound B Alq (100 Å) (400 Å) Example4 Compound A NPD Compound 21 (10%) Compound B Alq  (50 Å) (450 Å)Example 5 Compound A NPD Compound 39 (10%) Compound B Alq (100 Å) (400Å) Example 6 Compound A NPD Compound 40 (10%) Compound B Alq (100 Å)(400 Å) Comparative Compound A NPD Compound A (10%) Compound B AlqExample 1  (50 Å) (450 Å)

TABLE 2 VTE Device Results Rela- Rela- Relative Relative λ_(max) tivetive Initial LT80 x y (nm) Voltage EQE Luminance % Example 1 0.338 0.616528 1.1 0.9 0.8 0.8 Example 2 0.329 0.619 526 1.1 0.9 0.9 0.4 Example 30.391 0.583 538 1.3 0.9 0.8 1.3 Example 4 0.364 0.606 534 1.0 1.1 1.10.7 Example 5 0.357 0.607 532 1.1 0.8 0.9 0.7 Example 6 0.342 0.618 5281.0 1.0 1.0 0.5 Compara- 0.336 0.620 526 1.0 1.0 1.0 1.0 tive Example 1

Table 2 summaries the performance of the devices. The CIE coordinates,driving voltage (V), and external quantum efficiency (EQE) were measuredat 1000 nits, while the lifetime (LT_(80%)) was defined as the timerequired for the device to decay to 80% of its initial luminance under aconstant current density of 40 mA/cm². As can be seen from the table,despite the fused ring substitution, the inventive compoundsunexpectedly produced similar colors to the comparative example whilestill maintaining higher efficiency and longer device lifetime, whichmake them suitable for commercial applications as green emitters tordisplay and lighting,

It is understood that the various embodiments described herein are byway of example only, and are not intended to limit the scope of theinvention. For example, many of the materials and structures describedherein may be substituted with other materials and structures withoutdeviating from the spirit of the invention. The present invention asclaimed may therefore Include variations from the particular examplesand preferred embodiments described herein, as will be apparent to oneof skill in the art. It is understood that various theories as to whythe invention works are not intended to be limiting.

We claim:
 1. A compound comprising a ligand L having the structure;

wherein B is a 5 or 6-membered carbocyclic or heterocyclic ring; whereinC is a condensed aromatic ring system having at least two carbocyclic orheterocyclic rings; wherein A-B represents a bonded pair of carbocyclicor heterocyclic rings coordinated to a metal M via a nitrogen atom inring A and an sp²-hybridized atom X⁶ in ring B; wherein A-C represents abonded pair of carbocyclic or heterocyclic rings; wherein R^(A) mayrepresent mono, di, or tri substitutions, or no substitution; whereinR^(B) may represent any number of substitution from mono to up to themaximum possible number of substitution on ring B, or no substitution;wherein R^(C) may represent any number of substitution from mono to upto the maximum possible number of substitution on ring C, or nosubstitution; wherein R^(A), R^(B), and R^(C) are independently selectedfrom the group consisting of hydrogen, deuterium, halide, alkyl,cycloalkyl, heteroalkyl, aralkyl, alkoxy, aryloxy, amino, silyl,alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl,carbonyl, carboxylic acids, ester, nitrite, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof; wherein X¹, X²,X³, X⁴, X⁵, and X⁶ are independently selected from carbon and nitrogen;wherein X⁷ is carbon; wherein at least one of R^(A) and R^(C)substituents adjacent to the bond between A and C is not hydrogen; andwherein the ligand L is coordinated to the metal M having an atomicnumber greater than
 40. 2. The compound of claim 1, wherein A ispyridine.
 3. The compound of claim 1, wherein B is phenyl.
 4. Thecompound of claim 1, wherein only one of R^(A) and R^(C) substituentsadjacent to the bond between A and C is not hydrogen.
 5. The compound ofclaim 1, wherein the R^(A) and R^(C) substituents adjacent to the bondbetween A and C is selected from the group consisting of hydrogen;deuterium; linear, branched and cyclic alkyl; and combinations thereof.6. The compound of claim 1, wherein the R^(A) and R^(C) substituentsadjacent to the bond between A and C are selected from the groupconsisting of hydrogen, deuterium, methyl, ethyl, propyl, 1-methylethyl,butyl, 1-methylpropyl, 2-methylpropyl, pentyl, 1-methylbutyl,2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl,2,2-dimethylpropyl, cyclopentyl, cyclohexyl, and combinations thereof.7. The compound of claim 4, wherein the only one of R^(A) and R^(C)substituents adjacent to the bond between A and C that is not hydrogenis selected from the group consisting of deuterium, methyl, ethyl, andcombinations thereof.
 8. The compound of claim 1, wherein the compoundhas the formula:

wherein L′ monoaniomc bidentate ligand; and wherein n is at least
 1. 9.The compound of claim 8, wherein n=1.
 10. The compound of claim 8,wherein n=2.
 11. The compound of claim 8, where L′ is selected from thegroup consisting of:

wherein: Y₁, Y₂ and Y₃ are C or N, ring E and Ring F are 5-membered or6-membered carbocycle or heterocycle, R′, R″, and R′″ are independentlyselected from the group consisting of hydrogen, alkyl, alkoxy, amino,alkenyl, alkynyl, aralkyl, aryl, and heteroaryl, X is selected from thegroup consisting of S, NZ, O, Se, BZ, CZZ′, and C=O, Z and Z′ areindependently selected from the group consisting of hydrogen, alkyl, andaryl, and R′, R″, and R′″ can join to form one or more fused rings. 12.The compound of claim 8, where L′ is


13. The compound of claim 1, wherein the compound is heteroleptic. 14.The compound of claim 1, wherein the compound is homoleptic.
 15. Thecompound of claim 1, wherein bond between A and C is formed between X²and X⁷.
 16. The compound of claim 1, wherein bond between A and C isformed between X³ and X⁷.
 17. The compound of claim 1, wherein C isselected from the group consisting of:

wherein A¹ to A⁸, Q¹ to Q⁶, B¹ to B⁸, J¹ to J¹², K¹ to K¹⁰ areindependently selected from the group consisting of C and N; wherein Xand Y are independently selected from the group consisting of O, S, NR′,and CR″R′″; and wherein R′, R″, and R′″ are independently selected fromthe group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, aralkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof.
 18. The compound of claim14, wherein C is selected from the group consisting of:


19. The compound of claim 1, wherein the compound is selected from thegroup consisting of:


20. A first device comprising a first organic light emitting device,further comprising: an anode: a cathode: and an organic layer, disposedbetween the anode and the cathode, comprising a compound comprising aligand L having the structure:

wherein B is a 5 or 6-membered carbocyclic or heterocyclic ring; whereinC is a condensed aromatic ring system having at least two carbocyclic orheterocyclic rings; wherein A-B represents a bonded pair of carbocyclicor heterocyclic rings coordinated to a metal M via a nitrogen atom inring A and an sp² hybridized atom X⁶ in ring B; wherein A-C represents abonded pair of carbocyclic or heterocyclic rings; wherein R^(A) mayrepresent mono, di, or tri substitutions, or no substitution; whereinR^(B) may represent any number of substitution from mono to up to themaximum possible number of substitution on ring B, or no substitution;wherein R^(C) may represent any number of substitution from mono to upto the maximum possible number of substitution on ring C, or nosubstitution; wherein R^(A), R^(B), and R^(C) are independently selectedfrom the group consisting of hydrogen, deuterium, halide, alkyl,cycloalkyl, heteroalkyl, aralkyl, alkoxy, aryloxy, amino, silyl,alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl,carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof; wherein X¹, X²,X³, X⁴, X⁵, and X⁶ are independently selected from carbon and nitrogen;wherein X⁷ is carbon; wherein at least one of R^(A) and R^(C)substituents adjacent to the bond between A and C is not hydrogen; andwherein the ligand L is coordinated to the metal M having an atomicnumber greater than
 40. 21. The first device of claim 20, wherein thefirst device is a consumer product.
 22. The first device of claim 20,wherein the first device is an organic light-emitting device.
 23. Thefirst device of claim 20, wherein the first device comprises a lightingpanel.
 24. The first device of claim 20, wherein the organic layer is anemissive layer and the compound is an emissive dopant.
 25. The firstdevice of claim 20, wherein the organic layer is an emissive layer andthe compound is a non-emissive dopant.
 26. The first device of claim 20,wherein the organic layer further comprises a host.
 27. The first deviceof claim 26, wherein the host comprises a triphenylene containingbenzo-fused thiophene or benzo-fused furan; wherein any substituent inthe host is an unfused substituent independently selected from the groupconsisting of C_(n)H_(2n+1), OC_(n)H_(2n+1), OAr₁, N(C_(n)H_(2n+1))₂,N(Ar₁)(Ar₂), CH=CH—C_(n)H_(2n+1), C=CC_(n)H_(2n+1), Ar₁, Ar₁-Ar₂,C_(n)H_(2n)-Ar₁, or no substitution; wherein n is from 1 to 10; andwherein Ar₁ and Ar₂ are independently selected from the group consistingof benzene, biphenyl, naphthalene, triphenylene, carbazole, andheteroaromatic analogs thereof.
 28. The first device of claim 26,wherein the host comprises a compound selected from the group consistingof carbazole, dibenzothiphene, dibenzofuran, dibenzoselenophene,azacarbazote, aza-dibenzothiophene, aza-dibenzofuran, andaza-dibenzoselenophene.
 29. The first device of claim 26, wherein thehost is selected from the group consisting of:

and combinations thereof.
 30. The first device of claim 26, wherein thehost comprises a metal complex.
 31. A formulation comprising a compoundaccording to claim 1.